Process for bleaching sulphuric acid



Patented Apr. 21, 1925.

1,534,226 PATENT OFFICE.

wILLiAm CLELAND LEoNHARD, or PASSAIC, JOHlN ROY DUFFORD, or rarnason, AN ARTHUR HOUGH, F SUMMIT, NEW JERSEY.

PROCESS FOR BLEACHING SULPHURIC ACID.

No Drawing.

ticularly sulphuric acid containing snbstan tial amounts of organic matter, by means of electrolysis.

The process is applicable to the treatment of acid containing organic matter whether this is in the form of carbo-hydrates, more or less decomposedcarbohydrates, pure carbon, hydro-carbons, or other similar materials', and will be particularly described with relation to the treatment of sulphuric acid which has been used for parchmentizmg paper. The process stated, broadly consists in the decomposition of-water n the presence of sul huric acid and a manganese salt and organic matter as abovedescribed.

. The manganese sulphate has been found tobe most satisfactory'but other manganese salts or'compounds can be used, such as the chlorid nitrate, carbonate etc., which compounds would be converted into the sulphate during the process. The quantity of man- ,86 ganese sulphate necessary to produce best results may vary within'certain limits and may be as low' as. .25 of 1% or as high as 2% of the sulphuric acid undergoing treatment. Larger quantities e. g. 2% can be 40 used. It has been found that A of 1% .of

the manganesesulphate gives very good results with a. consumptionof electrical energy well within economical operating limits. The manganese sulphate is not reduced in 4 quantity only to the extent of that lost mechanically by factory operations such as the amount of sulphuric acid lost during the process of washing the parchment paper.

It has been found that the nascent oxygen evolved at the surface of the anode in thecell acts on the manganese sulphate producing permanganic acid. This'permangenie acid reacts on the organic matter and as an ultimate roduct we have manganese sulphate repr uced' quantitatively. By

Application filed January 18, 1924. Serial No. 687,123.

this means, the organic matter present in the sulphuric acid is oxidized with production of CO and without any loss: whatever of the original quantity of manganese salt em ployed with the exception of such losses as may result from factory operations above referred to. T v To carry out this invention and for the production of best results, it is preferable to have the sol huric acid of a's trength not below 40% H 0 and not higher than H 80 The temperature of this acid should be in the neighborhood of 80 to 100 centigrade, if lead peroxide anodes are used. If platinum, gold, orother materials, such 7 as magnetite, are used for the anodes, then the temperature of the acid must be in the nei hborhood of 130 centigrade. It is prefera 1e to use electrodes with a ratio of anode surface to cathode surface, four to one. The current density best suited for this work has been found to be about one-fifth of an ampere per square inch of anode surface, althon'gh this current density may be varied within 'wide limits and with good results.

The end oint is reached when the acid assumes as 'ght pink color which is an -indication that practically all the organic matter has been oxidized. On standing a short time this pink color disappears and the acid is bleached. It has been found that the bestmaterial for the anodes is electrolytic peroxide of lead and, by this, we refer to the hydrated eroxide of lead resulting from the electro ytic oxidation on a lower oxide 90 such as the protoxide or litharge, PbO as it is commonly termed.

As the particular form and method of construction of this type of anode forms the subject matter of a se arate invention it will 96 not be described in this specification but this patent is understood to cover the use of electrolytic peroxide of lead in connection with this new and improved bleaching process.

We claim 1. A process of bleaching sulphuric acid I containing organic matter which comprises the ste of ssing a current of electricity throng sucl i sulphuric acid containing a small percentage of manganese compound 106 in solution.

2. A process of bleaching sul huric acid containing organic matter in t e form of carbon ins'uspension which comprises the steps of adding a small proportion of man-.110

ganeee sulphate and pas through the acid an electric current un 'l such organic matter has been substantially removed.

3. A process of bleaching sulphuric acid containin organic matter'in the form of a. hydro-calion which comprises p an electric current through the acid containing manganese compound.

4. A process of bleaching sulphuric acid containin organic matter in the form of a hydro-car n which comprises pasing an electric current through the acid containing a small percentage of manganese sulphate.

5. A process of bleaching sulphuric acid containing a carbo-hydrate which comprises passing an electric current through the acid containing manganese sulphate.

6. A process of bleaching sulphuric acid containing organic compound which comprises passing an' electric current through the sulphuric acid containing a manganese salt employing anodes consisting largely of electrolytically prepared peroxide of lead.

7. A process of leaching sulphuric acid containing organic matter by passing an electric current through the acid containing a manganese salt and employing electrodes,

the anodes having a larger surface than the than the cathodes.

9. A. process of bleaching sul huric acid containing organic matter whic comrises passing'a current of electricity throng the acid containing a manganese-salt using'electrodes of any suitable material.

- 10. A process of bleaching sulphuric acid containingorganic matter which com rises passing a current of electricity throng the acid containing manganese sulphate usin electrodes of any suitable material.

I In testimony whereof we affix our signe tures in presence of two witnesses.

WILLIAM OLELAND LEONHARD. JOHN ROY DUFFORD. HOUGH.

Witnesses: A. H. Vnnmzmnn,

PJNEWMAN. 

